Gene flow from weedy rice to T1c-19 transgenic rice stacked with cry1C*/bar genes and fitness of F hybrids.

INTRODUCTION

Bidirectional gene flow via pollen between transgenic rice and weedy rice could occur in natural fields. Gene flow from transgenic rice to weedy rice has been confirmed in many studies, and thus results showed that F hybrids could persist in natural agroecosystems due to their unimpaired reproductive ability. However, the reverse gene flow from weedy rice to transgenic rice is rarely reported.

METHOD

We quantified reverse gene flow from three weedy rice accessions to transgenic rice line T1c-19 with cry1C*/bar. In field trials with alternating layout of cultivating transgenic rice and weedy rice accessions and adjacent layout cultivating them in a close vicinity, the reverse gene flow was detected. And the fitness of reverse F (RF) hybrids obtained by manual pollination using T1c-19 as maternal plants and weedy rice as paternal plants was evaluated in field.

RESULT

No gene flow from WRTZ was observed, while gene flows from WRMM were observed at 0.0508% and 0.0808%, respectively, and those from WRYY were 0.0692% and 0.1008%, respectively. RF plants exhibited significantly higher composite fitness compared to their weedy rice counterparts, due to enhanced fecundity-related traits observed under both insect pressure and no-insect pressure conditions. However, the impact of reverse gene flow may be limited because RF hybrid seeds presented lower seed shattering, and therefore most of it would be harvested by combine harvester.

DISCUSSION

Our study revealed that gene flow from three weedy rice accessions to T1c-19 could produce RF hybrids with greater composite fitness. Any loss of seeds into agroecosystem may result in a greater risk of RF1 hybrids due to their morphological similarity and high fitness.